Conventionally, before reading or writing data in an optical disk device, it is necessary to read disk information on the innermost end of a disk after power is turned on. However, an optical pickup is not always placed on a predetermined point because of disturbance. Thus the optical pickup is moved to one of the outermost end and the innermost end of the disk to adjust the offset of the position of the optical pickup, and then a reading sequence is started. In this movement to one of the outermost end and the innermost end, an optical sensor and a contact switch have been used to detect arrival at a destination. However, these components are more expensive than motor driver ICs. In order to reduce the cost of the overall optical disk device, a stop determination function is provided for the motor driver IC of a stepping motor and components required as detectors have been reduced. It is detected that an induced voltage is not outputted when the optical pickup reaches the innermost end and the outermost end, the optical pickup is made unmovable by a stop member, and the rotor of the stepping motor is locked. Further, the occurrence of an induced voltage in a normal rotation is detected. In the prior art, however, the detection of an induced voltage requires a high impedance section in an energization pattern and affects an energization waveform, causing a loss of synchronization of the rotor, vibrations, noise, and higher power consumption.
A technique relating to the present invention is, for example, described as a patent document in JP2005-27370A2. In order to detect the state of a rotor, a detection state setting unit is provided for setting a detection state in which one motor coil of two phases is cut off when the other coil can be energized, an induced voltage detecting unit is provided for detecting the induced voltage of the one coil, and a rotor state determination unit for determining the state of the rotor based on the detected induced voltage. With this configuration, the state of the rotor is determined based on the state of the induced voltage which is generated during the movement of the rotor.